linux-kernel - Re: [PATCH AUTOSEL 6.0 11/16] ACPI / PCI: fix LPIC IRQ model default PCI IRQ polarity

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Message-ID: <86pmchq4y9.wl-maz@kernel.org>
Date:   Sat, 17 Dec 2022 18:07:42 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jianmin Lv <lvjianmin@...ngson.cn>,
        Huacai Chen <chenhuacai@...ngson.cn>, bhelgaas@...gle.com,
        rafael@...nel.org, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.0 11/16] ACPI / PCI: fix LPIC IRQ model default PCI IRQ polarity

On Sat, 17 Dec 2022 15:28:14 +0000,
Sasha Levin <sashal@...nel.org> wrote:
> 
> From: Jianmin Lv <lvjianmin@...ngson.cn>
> 
> [ Upstream commit d0c50cc4b957b2cf6e43cec4998d212b5abe9220 ]
> 
> On LoongArch based systems, the PCI devices (e.g. SATA controllers and
> PCI-to-PCI bridge controllers) in Loongson chipsets output high-level
> interrupt signal to the interrupt controller they are connected (see
> Loongson 7A1000 Bridge User Manual v2.00, sec 5.3, "For the bridge chip,
> AC97 DMA interrupts are edge triggered, gpio interrupts can be configured
> to be level triggered or edge triggered as needed, and the rest of the
> interrupts are level triggered and active high."), while the IRQs are
> active low from the perspective of PCI (see Conventional PCI spec r3.0,
> sec 2.2.6, "Interrupts on PCI are optional and defined as level sensitive,
> asserted low."), which means that the interrupt output of PCI devices plugged
> into PCI-to-PCI bridges of Loongson chipset will be also converted to high-level.
> So high level triggered type is required to be passed to acpi_register_gsi()
> when creating mappings for PCI devices.
> 
> Signed-off-by: Jianmin Lv <lvjianmin@...ngson.cn>
> Reviewed-by: Huacai Chen <chenhuacai@...ngson.cn>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/20221022075955.11726-2-lvjianmin@loongson.cn
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/acpi/pci_irq.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index 08e15774fb9f..ff30ceca2203 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -387,13 +387,15 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
>  	u8 pin;
>  	int triggering = ACPI_LEVEL_SENSITIVE;
>  	/*
> -	 * On ARM systems with the GIC interrupt model, level interrupts
> +	 * On ARM systems with the GIC interrupt model, or LoongArch
> +	 * systems with the LPIC interrupt model, level interrupts
>  	 * are always polarity high by specification; PCI legacy
>  	 * IRQs lines are inverted before reaching the interrupt
>  	 * controller and must therefore be considered active high
>  	 * as default.
>  	 */
> -	int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ?
> +	int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ||
> +		       acpi_irq_model == ACPI_IRQ_MODEL_LPIC ?
>  				      ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW;
>  	char *link = NULL;
>  	char link_desc[16];

This is pointless on its own too, as it requires plenty of other
changes, none of which are stable candidates. Please drop this as well
as the v6.1 backport.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.